1. Field of the Invention
The present invention relates to a method of manufacturing a flow channel substrate for a liquid ejection head.
2. Description of the Related Art
Conventionally, as an image forming apparatus, an inkjet recording apparatus (inkjet printer) is known, which comprises an inkjet head (liquid ejection head) having an arrangement of a plurality of nozzles for ejecting ink and which forms images on a recording medium by ejecting ink from the nozzles toward the recording medium, while causing the inkjet head and the recording medium to move relatively to each other.
An inkjet head guides ink from an ink tank to ink chambers (pressure chambers) which are connected to nozzles, by means of ink flow channels, and ejects ink from the nozzles by various methods, for instance, by generating a pressure inside the ink chamber.
In this case, if air bubbles which may have entered inside the ink flow channels or which have occurred inside the ink flow channels adhere to positions such as corners of the end portions inside the ink flow channels, then ejection defects may occur since the ink is not supplied correctly.
Therefore, it is sought to form the ink flow channels in such a manner that the air bubbles can be expelled readily rather than adhering to the ink flow channels, even if air bubbles occur inside the ink flow channels.
In response to this, Japanese Patent Application Publication No. 9-193405, for example, discloses technology in which the corners of the cross-sectional shape of the ink flow channels can be formed with a rounded shape rather than an angled shape, in such a manner that the air bubbles are not liable to adhere to the ink flow channels but are removed readily.
In the technology described in Japanese Patent Application Publication No. 9-193405, as shown in (a) of FIG. 12, firstly, a resin layer (sacrificial layer) 504 which can be dissolved by a certain liquid (dissolving liquid) and has a rectangular cross-section is formed as an ink flow channel pattern on a substrate 500 on which a heat-generating resistor 502 is provided. Next, as shown in (b) of FIG. 12, this structure is subjected to heat treatment, and a rounded shape is applied to the corner section of the ink flow channel pattern of the sacrificial layer 504 which is formed in a rectangular shape. Next, a coating resin layer 506 which is not dissolved by the dissolving liquid is formed thereon, an ink ejection port 508 is formed in the portion of the coating resin layer 506 which corresponds to the portion vertically above the heat-generating resistor 502, and finally, the sacrificial layer 504 is dissolved away by the dissolving liquid and an ink flow channel 510 as shown in (c) of FIG. 12 is formed.
However, the technology described in Japanese Patent Application Publication No. 9-193405 entails a problem in that when a rounded shape is applied by means of heat treatment to the corner section of the ink flow channel pattern which is formed in a rectangular shape as the dissolvable resin layer, then the dissolvable resin layer (sacrificial layer) 504 becomes broader, as indicated by the reference symbol δ in (b) of FIG. 12, and hence the width of the portion contacting the substrate 500 changes and the dimensional accuracy becomes worse.
Moreover, since narrow corner sections 512 are formed in the corners of the flow channel 510, as shown in (c) of FIG. 12, due to the broadened portions of the sacrificial layer 504, then the air bubbles in the liquid (ink) tend to stay in these corner sections, the air bubble removal properties become worse, and this adversely affect the ejection of liquid.